Ultrasonic welding systems and methods using dual, synchronized horns on opposite sides of parts to be joined

ABSTRACT

An ultrasonic system and method for sealing a complex interface, such as a Gable top, having multiple and a variety of layers across the interface, or an oval or round spout having a complex geometry. The system includes two ultrasonic horns arranged opposite a gap between which the interface is provided. The frequency and phase of the ultrasonic energy are synchronized as the energy is applied simultaneously while the interface is pressed between a jaw and the energy is applied to both sides of the interface. Only one application of the frequency- and phase-synchronized ultrasonic energy is required to hermetically seal all the layers of the interface together.

BACKGROUND OF THE INVENTION

Certain types of packaging or containers can have complex sealinterfaces with a varying number of layers to be sealed along the sealinterface. The seal in some applications must be hermetic, air tight, ormust contain a liquid without any leaks. Conventional techniques to sealthese interfaces are extremely wieldy, expensive, and can requiremultiple passes over the same interface to complete the seal, requiringa lengthy amount of time for each item to be sealed. Some preparation ormanipulation of the item and/or its seal interface must also be carriedout before the seal can be formed. These preparations or manipulationscause additional delays in the sealing process.

Typically, these items can be composed of or coated with a plastic filmor a polyethylene material (e.g., liquid paperboard), such as pillowpacks, flow wraps, and cartons or other containers, such as milk cartonshaving so-called gable tops. To seal these items, conventionalapproaches can require different machines to seal different materials,take a relatively long time and can require multiple passes to create aleak-proof seal, suffer from inconsistent seals and can produce failedseals that produce channel leaks, produce waste, are incapable ofaddressing certain seal shapes, particularly narrow seals, and require alot of maintenance due in part to their complexity and number of movingparts.

In traditional ultrasonic welding, one ultrasonic stack is energized,and the part is pressed between the stack and a stationary anvil. Forcertain applications, this single-stack configuration poses challengeswhere the parts have multiple layers or other unusual geometries, andcan require multiple passes over the same part to create a high qualityseal or weld.

Gable top or other packaging sealing applications having an unevennumber of layers (such as 4-2-4-5 layers across a width of an interfaceto be sealed) exemplifies the inadequacy of using a single-stack horn.Suppose each carton layer absorbs or attenuates about 10% of the appliedultrasonic energy/amplitude. By the time traditional welding getsthrough 4-5 layers, there will only be about 50% of the ultrasonicenergy/amplitude remaining at the last layer, which is not enough toproduce a reliable seal. If the force or amplitude or time wereincreased to compensate for this energy loss, there is a risk ofover-welding the 2-layer section and possibly burning the externalsurface leaving a visual artifact on the product.

Round or oval interfaces, like spouts or ports, are very challenging toseal using conventional ultrasonic welding techniques. Usually,conventional techniques require many horns (e.g., up to four) andmultiple repeating movements of the horns, e.g., three steps or more) toseal these types of parts. These configurations are bulky, complex, andintroduce delay into a manufacturing process by having to repeatultrasonic movements multiple times to carry out their welding orsealing task. A need exists, therefore, for a solution that solves theseand other problems. Aspects of the present disclosure are directed tofulfilling these and other needs using ultrasonic energy in a one-passapplication to create a seal on a part, such as on a Gable top of acarton.

SUMMARY OF THE INVENTION

According to an aspect of the present disclosure, an ultrasonic weldingsystem for sealing together multiple layers of a part includes: a firstultrasonic welding stack including a first horn and a second ultrasonicstack including a second horn, the first horn having a first weldingsurface, the second horn having a second welding surface opposing thefirst welding surface to define a gap therebetween, wherein the gap isconfigured to receive therein the part to be sealed along a section ofthe part; an actuator assembly operatively coupled to the first andsecond ultrasonic welding stacks and configured to cause the firstwelding surface to move relative to the second welding surface; one ormore controllers operatively coupled to the first and second ultrasonicwelding stacks and to the actuator assembly, the one or more controllersoperatively being configured to: cause the actuator assembly to urge thefirst and second welding surfaces of the first and second horns towardone another until contacting the part, and thereby apply toward the parta first ultrasonic energy via the first horn and a second ultrasonicenergy via the second horn such that a frequency and a phase of thefirst and second ultrasonic energies are synchronized as the first andsecond ultrasonic energies are applied on both sides of the partsimultaneously, to thereby the seal the part along the section.

The frequency can be between 15 kHz and 70 kHz. The part can be a gabletop having a different number of layers arranged across a longitudinaldirection of the gable top. Alternately, the part can be a gable tophaving a different number of layers arranged across a directiontransverse to a longitudinal direction of the gable top. An amplitude ofthe first ultrasonic energy can be the same as or can differ from anamplitude of the second ultrasonic energy.

The system can further include a first generator generating the firstultrasonic energy and a second generator generating the secondultrasonic energy, wherein the first generator is designated as a mastergenerator that auto-locks feedback from the first ultrasonic weldingstack using a phase lock loop to itself and instructs the secondgenerator that acts as a slave generator to match its own phase andfrequency feedback to that generator by the first generator.

The part can be composed of a material that includes a polymeric film, athermoplastic material, a non-woven material, a metal foil, or a metal.The part can be a pillow pack having an end portion having a differentnumber of layers arranged across a longitudinal direction of the endportion. The part can include a different number of layers thatincludes, along the section of the part to be sealed, a first number oflayers in a first portion of the section and a second number of layersin a second portion of the section, the first number differing from thesecond number.

The apparatus can be a pillow pack or a carton or a pouch. The part canbe a spout to be sealed to a pouch.

The first horn can be a rotary horn and the second horn can be a rotaryhorn. The controller can be further configured to rotate the first hornand the second horn at the same rotational speed while applying thesynchronized first and second ultrasonic energies to the part.

The first generator can include a first output and a second output, thefirst output can be operatively connected to a first transducer and thesecond output can be operatively connected to a second transducer. Thefirst transducer can be operatively connected to the first horn and thesecond transducer can be operatively connected to the second horn.

An area of the part to be joined by far-field welding can be at least ¼inch or 6 mm away from the first welding surface of the first horn orfrom the second welding surface of the second horn.

According to another aspect of the present disclosure, an ultrasonicwelding method for sealing together multiple layers of a part includesthe steps of: moving a first welding surface of a first horn toward anopposing a second welding surface of a second horn to close a gapbetween the first welding surface and the second welding surface untilthe first and second welding surfaces contact a part to be sealed alonga section thereof; responsive to contacting the part, applying to thepart a first ultrasonic energy via the first horn and a secondultrasonic energy via the second horn such that a frequency and a phaseof the first and second ultrasonic energies are synchronized as thefirst and second ultrasonic energies are applied on both sides of thepart simultaneously, to thereby seal the part along the section, thefirst and second horns being arranged to point toward one another.

The method can further include, responsive to sealing the layerstogether, retracting the first horn relative to the second horn torelease the part. The frequency can be between 15 kHz and 70 kHz. Themoving can be caused by a rotational movement of the first horn rotatingat the same speed as a rotational movement of the second horn.

An amplitude of the first ultrasonic energy can be the same as or candiffer from an amplitude of the second ultrasonic energy. An apparatushaving at least one seal applied by the methods disclosed herein is alsocontemplated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an ultrasonic welding system for sealing togethermultiple layers of a part.

FIG. 2 illustrates a pillow pack and the number of different layers tobe sealed along its ends to create a hermetically sealed package.

FIG. 3A illustrates a carton in various configurations showing thenumber of folds needed that creates the multiple layers in the Gable topof the carton.

FIG. 3B illustrates a close-up view of the top of a Gable top showingthe different layers present along the width, height, and depthdimensions of the Gable top.

FIG. 4A illustrates an example ultrasonic welding stack having dualhorns positioned directly opposite one another defining a gap betweenwhich the part is inserted to seal all the layers together.

FIG. 4B illustrates the ultrasonic welding stack of FIG. 4A with thehorns closed together. For ease of illustration to show the horns, thepart to be sealed has been removed from between the horns.

FIG. 5A illustrates a dual-stack setup configured to perform a“scrubbing” welding action using synchronized ultrasonic energy appliedthrough a respective horn of each stack.

FIG. 5B is a cross-sectional view showing respective side weldingsurfaces of two horns abutting one another to seal a part interposedtherebetween using synchronized ultrasonic energy applied through bothhorns simultaneously.

FIG. 5C illustrates an example configuration for carrying out ascrubbing-type welding action using synchronized ultrasonic energyapplied to opposing horns simultaneously.

FIG. 5D illustrates the same configuration shown in FIG. 5C except withthe two horns spaced a distance apart to receive in the gap therebetweenan interface of a part to be sealed or joined together usingsynchronized ultrasonic energy applied to dual horns simultaneously.

FIG. 6A illustrates another example configuration to seal or join aspout or non-flat structure to a part using synchronized ultrasonicenergy applied to dual opposing horns simultaneously.

FIG. 6B is a top, perspective view of a top welding surface of a bottomone of the horns showing a grooved pattern corresponding to a spout ornon-flat structure to be joined using synchronized ultrasonic energyapplied to dual opposing horns simultaneously.

FIG. 6C is a front view of the two horns shown in FIG. 6A having a part,such as a spout, inserted between an opening that exists between the twohorns when they are pressed against one another.

FIG. 7 are example waveforms of ultrasonic energy applied to a first anda second horn, which waveforms are synchronized in frequency and phaseaccording to aspects of the present disclosure.

FIG. 8A is an illustration of a front view of dual rotary-hornconfiguration, whose frequency, phase, and angular speed is synchronizedto weld or seal layers of a part, such as being composed of a non-wovenmaterial, together.

FIG. 8B is a rear view of the dual rotary-horn configuration shown inFIG. 8A.

DETAILED DESCRIPTION

A surprising result discovered by the inventors of the inventionsdisclosed herein is that a very good hermetic seal (against air andliquid) can be formed using dual horns that deliver energy at ultrasonicfrequencies when their frequencies and phases are synchronized.Advantageously, only one pass is needed to form the seal, and the sealcan be formed in as little as one second or less with a singleapplication of ultrasonic energy (e.g., 0.35 sec). The seals haveproduced no leaks and work especially well when the interface to besealed has a complex number of layers to be sealed together. Forexample, so-called Gable tops on milk cartons and the like can have aseal interface involving two layers on one end of the interface, up tofour layers in another section of the interface, and possibly fivelayers at the other end of the interface, depending on how the cartonblank is folded. The sealing problem becomes particularly challengingwhen trying to seal across an interface where different layers arepresent in different sections of the areas along the interface to besealed.

Examples of these complex interfaces to be sealed can be seen in FIGS.2-3 and 6C.

Ultrasonic transducers are devices that convert energy into sound,typically in the nature of ultrasonic vibrations—sound waves that have afrequency above the normal range of human hearing. One of the mostcommon types of ultrasonic transducers in modern use is thepiezoelectric ultrasonic transducer which converts electric signals intomechanical vibrations. Piezoelectric materials are materials,traditionally crystalline structures and ceramics, which produce avoltage in response to the application of a mechanical stress. Sincethis effect also applies in the reverse, a voltage applied across asample piezoelectric material will produce a mechanical stress withinthe sample. Suitably designed structures made from these materials cantherefore be made that bend, expand, or contract when a current isapplied thereto.

Many ultrasonic transducers are tuned structures that containpiezoelectric (“piezo”) ceramic rings. The piezo ceramic rings aretypically made of a material, such as lead zirconium titanate ceramic(more commonly referred to as “PZT”), which have a proportionalrelationship between their applied voltage and mechanical strain (e.g.,thickness) of the rings. The supplied electrical signal is typicallyprovided at a frequency that matches the resonant frequency of theultrasonic transducer. In reaction to this electrical signal, the piezoceramic rings expand and contract to produce large-amplitude vibrationalmotion. For example, a 20 kHz ultrasonic transducer typically produces20 microns of vibrational peak-to-peak (p-p) amplitude. The electricalsignals are often provided as a sine wave by a power supply thatregulates the signal so as to produce consistent amplitude mechanicalvibrations and protect the mechanical structure against excessive strainor abrupt changes in amplitude or frequency.

Typically, the ultrasonic transducer is connected to an optionalultrasonic booster and a sonotrode (also commonly called a “horn” in theultrasonic welding industry), both of which are normally tuned to have aresonant frequency that matches that of the ultrasonic transducer. Theoptional ultrasonic booster, which is structured to permit mounting ofthe ultrasonic transducer assembly (or “stack” as it is commonlycalled), is typically a tuned half-wave component that is configured toincrease or decrease the vibrational amplitude passed between theconverter (transducer) and sonotrode (horn). The amount of increase ordecrease in amplitude is referred to as “gain.” The horn, which isoftentimes a tapering metal bar, is structured to augment theoscillation displacement amplitude provided by the ultrasonic transducerand thereby increase or decrease the ultrasonic vibration and distributeit across a desired work area.

Typically, all of the mechanical components used in an ultrasonictransducer assembly must be structured so that they operate at a singleresonant frequency that is near or at a desired operating frequency. Inaddition, the ultrasonic transducer assembly must often operate with avibrational motion that is parallel to the primary axis (i.e., thecentral longitudinal axis) of the assembly. The power supply for thestack generally operates as part of a closed-loop feedback system thatmonitors and regulates the applied voltage and frequency.

For certain applications, particularly those involving welding ofthermoplastic parts together, ultrasonic welding technology is highlydesirable due to its consistency (particularly when the stack's movementis controlled by a servo-driven motor), speed, weld quality, and otheradvantages. The inventors have discovered that leveraging dual hornssynchronously applying ultrasonic energy to a complex interface having avariety of layers across the area to be sealed surprisingly produces anexcellent airtight and hermetic seal in one pass, by matching the phaseand frequency of the energy delivered through both horns and applyingthe energy on either side of the complex interface. Power to each hornis controlled by an ultrasonic generator that delivers consistent andreliable energy even in noisy environments to the horn. An example ofsuch an ultrasonic generator suitable for use in connection with thesystems and methods described herein is disclosed in U.S. Pat. No.7,475,801, the entirety of which is incorporated herein by reference,and a suitable ultrasonic generator is commercially available fromDukane under the brand name iQ™. Each horn can be driven by an iQ™ultrasonic generator or similar generator capable of outputting aconsistent and reliable ultrasonic energy signal through the horn to apart or parts to be welded or joined. Because the components andconfiguration of an ultrasonic generator would be well known to theskilled person familiar with ultrasonic welding, for the sake ofbrevity, a detailed description of these is omitted because they are notessential for an understanding of the inventions disclosed herein. Eachhorn (or technical the horn's transducer) can be powered by a separatepower supply, or they can be powered by a single power supply with dualpower outputs that can be independently controlled. The entire pass orcycle time from applying the force to the horns 106, 108 to removing theultrasonic energy can be very fast, e.g., 0.35 seconds or even fasterwith a higher amplitude of energy.

The force imparted to a part to be sealed can be adjustable within areasonable range, such as +/−50% from the nominal value for each sizemachine or part. The part's geometry, material, and expectations for thefinished product define choices in operating frequency (e.g., as ageneral rule, lower frequency and higher amplitude for larger parts,higher frequency and lower amplitude for smaller parts). In ultrasonicwelding there are essentially three parameters that need to be adjustedto get a high quality and consistent weld for a specific part: a)amplitude; b) force; and c) weld time (time during which ultrasonicenergy is applied to the part). Most applications call for a short weldtime to maximize yield, particularly in packaging applications wherehundreds or thousands of packages are filled and sealed per hour.Amplitude is often limited by stresses in the horn, so there is apractical limit as to how high the amplitude can be set. This leavesforce, but as force is increased to get a good weld quickly, too muchforce might constrain the movement of the ultrasonic stack and it can bedamaged or destroyed. Or the stack can get stuck akin to jaws closing asa brick wall. If the brick wall does not yield, then the movement of thestack will be difficult to maintain. A Gable top requires more force,whereas a pillow pack requires less force applied by the horns. Thinfilms would require a different ratio of amplitude and force, which canalso be based on the material and speed requirements. The systems andmethods disclosed herein allow for much more flexibility andsignificantly open the process window, meaning that the process becomesmore robust and less sensitive to the usual production variablescompared to conventional approaches.

FIG. 1 is an ultrasonic welding system 100 for sealing together multiplelayers of a part 110. The system 100 includes two ultrasonic weldingstacks (shown in FIGS. 4A and 4B) including a first transducer 102 and asecond transducer 104. The system 100 includes a first horn 106 having afirst welding surface 106 a opposing a second welding surface 108 a of asecond horn 108 defining a gap 112 between the first and second weldingsurfaces 106 a, 108 a. The gap 112 is configured to receive therein thepart 110 having a different number of layers to be sealed along asection of the part 110. The section of the part 110 to be sealed hasbeen shown in exaggerated expanded and slightly unfolded form in FIG. 1for ease of illustration to show the different number of layers presentin this example part 100 from left to right. In reality, these layerswould be pressed against one another when presented in the gap 112.Starting from the left in FIG. 1, as shown by the dashed lines, thefirst section of the part 110 to be sealed has four layers, followed bya second section having only two layers, followed by a third sectionhaving four layers, and finally ending by a fourth and last sectionhaving five layers. This type of interface is typically found in cartonshaving a Gable top such as shown in FIG. 3A. FIG. 3A shows an examplecarton in a fully assembled configuration, folded in half, andcompletely unfolded into a flat starting configuration. In the latterconfiguration, the complexity of the folds and layers can be seen in thetop of the flattened carton, in which five sections 340 a-f are present.When these are folded to form a Gable top 334, they produce an interfaceas shown in FIG. 1 with multiple layers. The area of the horn 106, 108that contacts the part to be sealed is referred to herein as a “weldingsurface,” meaning that it is a contacting surface of the horn that makescontact with the part to deliver via that surface the ultrasonic energyinto an interface to be sealed of the part to weld (or seal) theinterface. The ultrasonic energy passes through the horn away from thewelding surface and into the part that is contact the welding surface ofthe corresponding horn. Each welding surface 106 a, 108 a of the horns106, 108 makes physical contact with a different area of the part to bewelded (the part's sealing interface), e.g., in the case of a Gable top,on either side of the Gable top to be formed when all the layers aresealed together.

The interface to be sealed can not only have different numbers of layersacross its width but also across its height, as shown in FIG. 3B. Here,as the legend indicates, there are at least five sections 350 a,b,c,d,ethat need to be sealed together to form a hermetic seal. For example,along the elongated width dimension of the interface 110, 310 shown inFIG. 3B, there are four sections having, starting from left to right,four layers 350 b, then two layers 350 c, then four layers 350 d again,terminated by five layers 350 e. However, above these sections along aheight dimension, there is an elongated section 350 a having only twolayers. Thus, taken along the height dimension (which is transverse to alongitudinal direction of the Gable top 310), there is only one sectionin the middle of the interface 310 where two layers are present in thearea to be sealed. Everywhere else, there is a different number oflayers above and below the corresponding sections of the interface 310to be sealed. This type of Gable top 334 is particularly challenging toseal, because of the multi-dimensional changes in the number of layersacross its width, height, and depth (due to the varying thickness of thedifferent layers). Conventional adhesive-free methods are eithertime-consuming and require multiple passes along the interface, orsimply do not produce a hermetic seal that can prevent all liquid fromescaping. The carton 330 can also sometimes include a plastic spout 332protruding from the Gable top to facilitating pouring. The Gable top 334can be opened a la a milk carton for pouring out the liquid contents ofthe carton 334. The present disclosure is particularly well-suited forhermetically sealing Gable tops having many different layers in allthree dimensions.

Another type of part that has a similar type of interface to be sealedis a pillow pack 230, illustrated in FIG. 2, which has tops or ends thatresemble a Gable top. Pillow packs are usually first joined at a firstseam running lengthwise along the pack, which presents an area that hasmultiple layers. The ends 210 of the pillow pack 230 also have multiplelayers as shown by the legend. In this configuration, which is sometimesreferred to as a 4-2-4-2-4, there are four layers in a first section ofthe end 230, followed by two layers, then four layers again, followed bytwo layers, and finally four layers. The different number of the layersare thus arranged across a longitudinal direction of the Gable top 210of the pillow pack 230. Again, this type of part with a different numberof layers presents a particular challenge to seal. The synchronized dualhorn/stack configuration of the present disclosure can seal pillow packsso that they are airtight without any leaks. The pillow pack shown inFIG. 2 and the carton 330 shown in FIG. 3A can be composed of apolymeric film or a thermoplastic material.

Another type of part having interfaces that can be sealed using theinventions disclosed herein is a fluid-filled pouch having a valve or apierceable sealing element that can be pierced, e.g., by a straw, suchas described in U.S. Patent Application Publication No. 20040161171A1.An example system configured to seal using the ultrasonic technologydisclosed herein a fluid-filled type of pouch is shown and described inconnection with FIGS. 5A-5D. A popular type of pouch is sold in the U.S.under the brand CAPRISUN®. An example system configured to seal usingthe ultrasonic technology disclosed herein a part having a spout isshown and described in connection with FIGS. 6A-6C.

In liquid-filled pouches when a liquid is already present in the pouchbefore the pouch is sealed, the synchronized ultrasonic energy from thedual horns produces a vibration at the interface that pushes awayliquids from the interface area, further contributing to creating ahermetic seal. In other words, a surprising benefit of the applicationof dual synchronized ultrasonic energy to a part filled with liquid isthat the vibrations produced by the application of the energy from bothsides of a to-be-sealed interface tends to vibrate away any droplets ofliquid present around the interface, thereby allowing the layers of theinterface to be sealed together without getting liquid trappedtherebetween and creating opportunities for leaks. Microscopic leaksalso present a health and spoliation hazard, allowing bacteria or otherpathogens into the sealed pouch or mold to form around the seal. Bycreating a hermetic seal in one pass of the dual horns, wherein thevibrations produced by the application of ultrasonic energy from bothsides of an opening of a liquid-filled pouch shake off liquid at theinterface before being sealed, an additional advantage can be seen fromthe synchronized dual horn configuration disclosed herein.

Returning to FIG. 1, the system includes an actuator assembly 116operatively coupled to the ultrasonic welding stack (FIGS. 4A and 4B)and configured to cause the first welding surface 106 a of the firsthorn 106 to move relative to the second welding surface 108 a of secondhorn 108. The movement of the horns 106, 108 together can be aided bycorresponding frames 130, 132 to which the respective horns 106, 108 arecoupled, which frames 130, 132 form part of the actuator assembly thatmoves the horns 106, 108 together and apart from one another. Onemovement of the horns 106, 108 together to clamp a part to be sealed andthen apart following application of the ultrasonic energy to the part isreferred to as a single pass or cycle. The actuator assembly 116 caninclude one or more motors, such as a servo motor. The two weldingsurfaces 106 a, 108 a are directly opposed one another and form mutuallyparallel planes that are orthogonal to an orientation of the horns 106,108. The two horns 106, 108 can be seen as moving toward one anotherlike a jaw that opens and closes such that the exposed end weldingsurfaces 106 a, 108 a thereof contact corresponding opposite surfaces ofa part or part interface to be sealed. The corresponding ultrasonicenergy from the transducers 102, 104 imparted to the horns 106, 108,which is synchronized in frequency and phase, is outputted along thesame dimension in opposite directions. Each of the dual ultrasonicwelding stacks can include an optional booster 140, 142, shown in FIG.4A, which amplifies the energy emitted from the transducers 102, 104before passing into the horn 106, 108. Again, the presence of theboosters 140, 142 is optional, and the configurations shown in FIGS. 5Aand 6A lack a booster. In these configurations, the transducer 102, 104is mounted directly to the horns 506, 508 (FIG. 5A) and 606, 608 (FIG.6A).

A controller 120, which can be one or more controllers, is operativecoupled to the ultrasonic welding stacks and to the actuator assembly116. The controller 120 is configured to cause the actuator assembly 116to urge the first and second welding surfaces 106 a, 108 a of the horns106, 108 toward one another until contacting the part 110. Apredetermined force can be applied to the horns 106, 108 to essentiallyclamp the part 110 between the welding surfaces 106 a, 108 b and keepthe folded layers together. For example, the maximum force imparted bythe horns on the part 110 can be set at 4500N, but will depend on theapplication including the thickness of the interface and the materialsto be joined together. The controller 120 applies toward the part 110 afirst ultrasonic energy via the output of the first horn 106 and asecond ultrasonic energy via the output of the second horn 108 such thata frequency and a phase of the first and second ultrasonic energies aresynchronized as the first and second ultrasonic energies are applied onboth sides of the part 110 simultaneously, to thereby the seal thelayers together, such as the layers 350 a,b,c,d,e shown in FIG. 3B. Asmentioned above, an example ultrasonic generator suitable to generateultrasonic energy through a transducer into a horn is described in U.S.Pat. No. 7,475,801 and is commercially available from Dukane under anyof the iQ™ line of ultrasonic generators.

Synchronization of two ultrasonic generators can be accomplished byproviding a communication connection between the two generators so thattheir respective outputs to the transducers 102, 104 are synchronized infrequency and phase. Alternately, a generator such as the one describedin the patent above can be modified to provide two outputs that aresynchronized in frequency and phase and provided to a respectivetransducer 102, 104. The generators (whether separate or integrated withdual outputs) can be arranged in a master-slave relationship wherein oneof the generators is assigned to be a master. The phase of the mastergenerator is auto-locked to its ultrasonic stack's feedback using aPhase Lock Loop (PLL), and the master generator instructs the slave viathe communication connection to mimic the same phase at the zerocrossings (at 0 or 180 degrees) and ignore the slave's own phase andfrequency feedback. This allows the slave's phase to drift in the samemanner as the master. Phase drifts can occur, e.g., due to thermaleffects, so by locking the phase of the slave to the master allows thephase (and therefore by implication the frequency corresponding to thezero crossings of the ultrasonic energy signal's phase) to besynchronized in both transducers 102, 104.

FIG. 7 illustrates example waveforms, which are not to scale, ofsynchronized ultrasonic energy applied to the first transducer 102 andto the second transducer 104. Here, synchronized refers to the energyhaving the same frequency, f1, and phase. The amplitude, A, may or maynot be identical for both horns. Depending on the application and thethickness of the part closest to the horn 106, 108, a differentamplitude can be applied through the first horn 106 relative to thesecond horn 108. Just as the frequency, f1, is matched in both horns106, 108, so too the phase of both energies is time synchronized so thatthe zero-crossings and the peaks of the energy over time coincide at thesame time as shown by the dashed lines in FIG. 7. The frequency, f1, ofthe energy generated in one horn 106 (or transducer 102) can be within 3Hz of the energy generated in the other horn 108 (or transducer 104).Using two, synchronized horns halves the energy attenuation throughmultiple layers, such as when sealing a Gable top compared to a singlehorn setup. For example, in a single-stack configuration, the ultrasonicenergy must pass through 4-5 layers of a Gable top, producing up toabout a 50% attenuation or loss of ultrasonic energy/amplitude. Bycontrast, when using the synchronized dual horns according to thepresent disclosure, the energy from one horn only passes through 2 or2.5 layers (the energy from the other side similarly passes through onlyhalf the number of layers compared to a single-stack configuration), andhence the energy/amplitude losses are only about 20-25%, producing ahigh quality weld or seal without burning the layers or creating anyvisual artifacts on the outer surface of the interface being sealed.

It has been found that the frequency of the ultrasonic energy deliveredthrough both of the transducers 102, 104 to the horns 106, 108 isbetween about 15-70 kHz (e.g., ±10%). Particularly effective results areseen with 15 kHz, 20 kHz and 30 kHz. The frequency and phase of theultrasonic energy delivered through both transducers 102, 104 to thehorns 106, 108 to seal the part are synchronized in time so that peakamplitude of the ultrasonic energy is delivered simultaneously on bothsides of the part to be sealed. The amplitude of the ultrasonic energycan be controlled independently on both transducers 102, 104. Afrequency of 20-35 kHz is particularly suited for sealing smaller orthinner packaging, and higher frequencies can be used for sealing largeror thicker packaging.

An example “scrubbing” configuration is shown in FIGS. 5A-5D. In thisconfiguration, there are two transducers 102, 104 synchronized infrequency and phase just as in the previous configurations, but thehorns 506, 508 are positioned so that their sides come into contact topress against a to-be-sealed interface of a part, such as a thin filmhaving a thickness in a range of 10-20 um, or a thin, non-woven filmwhere the thickness can vary along the length of the interface. Thevariation in thickness can be ±2 um at unpredictable locations along thelength of the interface. Thus, while the application of energy may beuniform, the thickness of the interface (e.g., which can be composed ofjust two layers being sealed together) can vary along the length of theinterface being sealed together, creating opportunities for small leaksor uneven welding of the seal. The so-called scrubbing action leveragesthe tiny, mechanical Y-axis motions produced by the two horns 506, 508vibrating relative to one another as the frequency- andphase-synchronized ultrasonic energy is imparted through the transducers102, 104 to the horns 506, 508. These vibrations produce very short,rapid back and forth motions in the horns 506, 508 that resemble ascrubbing movement, which has been found to produce very high qualityhermetic seals where the interface has a non-uniform thickness, such aswhen the interface is a thin film or non-woven film. The configurationshown in FIGS. 5A-5D also allow for gentler control of amplitude andforce as applied to a thin interface, and a wider process window.

In FIG. 5A, two ultrasonic stacks, each including a transducer 102, 104and a horn 506, 508. The horns 506, 508 are positioned adjacent oneanother so that their respective side welding surfaces 506 a, 508 a movetoward one another. These welding surfaces 506 a, 508 a are parallel tothe Y-Z plane and extend along a length along the Z axis. The ultrasonicenergy is applied through the transducer 102 along the Y axis direction,and the ultrasonic energy through the second transducer 104 is appliedin the opposite direction along the Y axis direction. The side surfaces506 a, 508 a vibrate past one another as the part is positionedtherebetween and the frequency- and phase-synchronized ultrasonic energyis applied through the horns 506, 508 simultaneously. Thin film or thinnon-woven materials form a hermetic seal with only one pass ofultrasonic energy through the horns 506, 508. Only two horns 506, 508and a single pass are required to produce a consistent, hermetic seal,free from burns or visual artifacts or microscopic leaks. While a thinfilm or non-woven material has been described in these examples, thescrubbing aspects disclosed herein also work with welding metal films,metal foils or thin metals, or any combination of thin film, non-wovenmaterial, or metals. For example, scrubbing is particularly effective atsealing metals together, but also is effective at sealing dissimilarmaterials together, e.g., a non-woven material to a metal film or foil.

In FIG. 5B, a close-up of the two side welding surfaces 506 a, 508 a canbe seen of the horns 506, 508. The welding surface 506 a extends away toform a smaller exposed surface area compared to the flat side weldingsurface 508 a. In this way, the side welding surface 506 a acts as a“scrubber” as it moves rapidly back and forth along the Y-axis directionunder ultrasonic influence when a part 110 is positioned between the twohorns 506, 508. An example configuration can be seen in FIG. 5C, wherethe horns 506, 508 are in contact with one another. The part 110, whichfor example can be a pouch having an open end that needs to be sealed,has its open end positioned between the horns 506, 508, which would“scrub” the two layers of the interface together as the ultrasonicenergy is applied from opposite sides of the interface. The mechanicalaction coupled with the heat produced by the ultrasonic energiescooperate to produce a hermetic seal free from artifacts or microscopicleaks. FIG. 5D shows the horns 506, 508 spaced apart. The part'sinterface 110 is positioned in the gap between the two side weldingsurfaces 506 a, 508 a, which are urged toward one another along theX-axis direction until their side welding surfaces 506 a, 508 a contactwith opposite sides of the interface 110. A force is applied to thehorns 506, 508 while the ultrasonic energy is applied through thetransducers 102, 104 and into the horns 506, 508, producing the tinymechanical vibrations referred to as the scrubbing action along themelting of the interface 110 where the welding surfaces 506 a, 508 apress against it. Once the horns 506, 508 are retracted, a hermetic sealis present at the part's interface 110, requiring only one pass ormovement of the horns 506, 508 and one application of the synchronizedultrasonic energies.

Another synchronized dual-horn configuration is shown in FIGS. 6A-6C,which is suitable for sealing parts having complex geometries, such as aplastic or metal spout for a liquid pouch, pillow, or container. Here,two transducers 102, 104 are positioned relative to a first contouredhorn 606 and a second contoured horn 608 having an opening 612 (bestseen in FIG. 6C) to receive therein a part 332 to be sealed. The end ofthe horns 606, 608 have a knurled surface 608 b (best seen in FIG. 6B),to clamp around the part 332 (which can be a round spout, for example),which transition to a ribbed welding surface 608 a that receives theround (or oval) part 332. The other horn 608 has the same weldingsurfaces, so that they press against one another, the part 332 is heldin place and a uniform application of energy is evenly distributedaround the part to produce a consistent weld. The contoured horns 606,608 can be shaped to match the contour of any part's geometry, includinground, oval, or any irregular geometry.

A further dual-horn configuration is schematically illustrated in FIGS.8A and 8B. Two horns 806, 808 are of the rotary type, and those familiarwith the art of ultrasonic welding will appreciate rotary horns and howthey are driven, the details of which are not pertinent to anunderstanding of this configuration. An example of a configurationincluding a rotary horn and a stationary anvil is shown in U.S. Pat. No.10,479,025, granted Nov. 19, 2019, and entitled “Apparatus forfabricating an elastic nonwoven material,” the entirety of which isincorporated herein by reference. According to the concepts disclosedherein, two rotary horns 806, 808 are proposed as shown in FIG. 8A, inwhich both horns 806, 808 contact both sides of a part 810 havingmultiple layers 840 a, 840 b (though more than two are contemplated),such as a non-woven material having multiple layers to be joined orsealed together, which passes between the two horns 806, 808 as thehorns are rotating at the same angular speed, ω1. The frequency andphase of the respective ultrasonic energies being imparted to the horns806, 808 are synchronized, as disclosed herein, producing a high qualityseal or joining of the layers 840 a, 840 b of the part 810 in one passthrough the horns 806, 808. A force can be applied to the layers 840 a,840 b of the part 810 between the horns 806, 808, as the part 810 passestherebetween. For ease of illustration, the physical separation betweenthe layers 840 a, 840 b has been exaggerated in FIGS. 8A and 8B to showhow they are joined together by the dual rotary horns 806, 808, whichare driven by respective transducers 102, 104. Each of the transducers102, 104 is powered by corresponding outputs of one or more ultrasonicgenerators as described above that produce ultrasonic energy outputs toboth transducers 102, 104 that is synchronized in both frequency andphase. Thus, in this configuration, and angular speed ω1 of the hornsand frequency and phase of the ultrasonic energy applied to each hornare synchronously matched.

The layers 840 a, 840 b of the part 810 are drawn between the two horns806, 808, which are rotating at the same angular speed as ultrasonicenergy having the same frequency and phase is imparted to both horns806, 808 simultaneously. By applying ultrasonic energy matched infrequency and phase to both horns 806, 808 simultaneously allows theamplitude of the energy to be reduced compared to a configuration havingonly one energized stack, which produces higher throughput (e.g.,exceeding 2000 feet per minute) while expanding the process window.

An ultrasonic welding method for sealing together multiple layers(forming a to-be-sealed interface) of a part is also disclosed. Themethod includes moving a first welding surface of a first horn toward anopposing a second welding surface of a second horn to close a gapbetween the first welding surface and the second welding surface untilthe first and second welding surfaces contact a part, such as a parthaving a different number of layers along a section of the part to besealed. Responsive to contacting the part, the method applies toward thesection of the part between the two horns a first ultrasonic energy viaan output of a first horn and a second ultrasonic energy via an outputof a second horn such that a frequency and a phase of the first andsecond ultrasonic energies are synchronized as the first and secondultrasonic energies are applied on both sides of the partsimultaneously, to thereby seal the layers together. The respectiveoutput tips of the first and second horns are arranged to point towardone another. Importantly, the closing and retraction of the horns occursonly one time to seal the interface without causing any burns, visualartifacts, or leaving any air or liquid leaks along the interface. Bycontrast, conventional approaches require multiple horn movements (e.g.,three or more) to create a seal, which is time consuming and increasesthe risk of burning parts of the interface or creating undesirablevisual artifacts particularly in thinner areas of the interface (e.g.,when sealing a gable top).

Aspects of the present disclosure are also applicable to so-calledfar-field welding where the area to be welded is located a physicaldistance away from the horn output or surface from which the ultrasonicenergy transitions from a solid substrate into the area outside thehorn. In many applications, the location of the joint in regard to thearea of horn contact can be critical, because the ultrasonic energy musttravel through the material to reach the desired area of melt.Near-field and far-field welding refer to the distance that ultrasonicenergy is transmitted from the point of horn contact to the jointinterface. For example, when the distance between the horn output orsurface and the joint interface to be welded is ¼″ (6 mm) or less, itcan be considered near field. By contrast, when the distance is greaterthan ¼″ (6 mm), the weld can be considered far field. Whenever possible,it is always best to weld near field. This is because far-field weldingrequires higher than normal amplitudes, longer weld times, and higherforces to achieve a comparable near-field weld. Generally speaking,far-field welding is advised only for amorphous resins, which transmitenergy better than semi-crystalline resins. However, with the two-hornconfiguration disclosed herein, the applications for far-field weldingcan be expanded because the energy is being applied from two sides of aninterface simultaneously.

The dual horn aspects disclosed herein are also applicable toultrasonic-assisted metal wire drawing processes or ultrasonic-assistedmetal forming processes. Conventional metal drawing or forming processescontemplate using one source of ultrasonic energy applied to a hardsteel die or the like as the wire or metal is pulled through the die.The pulling force is very high and eventually the die dulls and requiresreplacement. The present disclosure contemplates applying ultrasonicenergy synchronized in frequency and phase to two sides of the diesimultaneously as the wire or metal is drawn through the die by anexternal pulling force. The energy produces vibrations in the die,causing the die to act as a lubricant, thereby reducing the forcesrequired to draw the wire through the die. The die will requirereplacement at a longer time interval, improving throughput forprocesses involving metal wire drawing or metal forming.

While some materials have been described herein as being suitable forsealing or welding using the synchronized dual-horn ultrasonic energyapplications disclosed herein, including plastic and non-woven film, thepresent disclosure contemplates sealing or welding other types of sameor dissimilar materials together, including pouches made from polyesterprinted to aluminum then laminated to polyethylene, metal includingaluminum, metal foil, fabric, film, polyethylene-coated fiberboard orliquid paperboard, and the like.

Advantages of the systems and methods disclosed herein include:

Process speed increase: compared to conventional ultrasonic weldingtechniques that require multiple cycles and applications of ultrasonicenergy, the systems and methods herein require only one cycle to createa hermetic seal for a variety of packaging, geometries, and materials.

Seal through same or dissimilar materials: a hermetic seal is formedthrough one application of synchronized ultrasonic energy impartedthrough two opposing horns, regardless of the material or its thicknessuniformity.

Consistency, repeatability in weld results with wider process windowparameters: Because two horns are applying the same ultrasonic energy(same frequency and phase) simultaneously, this effectively doubles theamplitude of the energy, enabling wider process window parameterscompared to conventional techniques.

Housekeeping in production area, greener process (ultrasonic weldingrequires a lot less energy than heat seal technology): compared toheat-seal technologies that require application of heat energy to createa seal, ultrasonic energy by comparison utilizes less energy, creating aseal in a fraction of a second, such as 0.35 seconds or even faster.

Enable use of new materials, including bioplastics and material withpoor welding compatibility: the dual horn setup synchronized tofrequency and phase, and optionally coupled with the scrubbing actionproduced by the vibrations of the horns, significantly expands theavailable combinations of materials, interfaces, and geometriesavailable for creating consistently high quality and hermetic seals orwelds.

Waste and delay reduction; yield improvements: conventional techniquesproduce inconsistent seals, sometimes with tiny leaks, or can createburns or other visual artifacts requiring that some parts be discarded,lowering overall yield.

Narrower seal producing material savings: the interface or area to besealed can be quite small compared to conventional techniques, allowingless overall material to be used. When millions of parts are beingsealed or welded, a small reduction in material per part can yield asignificant reduction in overall material.

Eliminate channel leaking: conventional techniques can produce tinyleaks that can create opportunities for air, pathogens, and/or mold tobe present, but systems and methods of the present disclosure eliminateleaks without creating any visual artifacts and without causing burns atthe interface of the seal.

Reducing manufacturing process complexity as for example welding spoutto pouches can be done in one pass or cycle with this technology. Bycomparison, the same spout-to-pouch welding is currently being carriedout in three passes or cycles with conventional ultrasonic weldingtechnology.

Eliminate liquid or product contamination in the joint area due toultrasonic energy (vibrations) from the ultrasonic stacks. It can alsoeliminate liquid content between two joints on vertical or horizontalpackaging machines, where liquid is not desirable (e.g., in a brickcarton assembly line).

What is claimed is:
 1. An ultrasonic welding system for sealing togethermultiple layers of a part, the system comprising: a first ultrasonicwelding stack including a first horn and a second ultrasonic stackincluding a second horn, the first horn having a first welding surface,the second horn having a second welding surface opposing the firstwelding surface to define a gap therebetween, wherein the gap isconfigured to receive therein the part to be sealed along a section ofthe part; an actuator assembly operatively coupled to the first andsecond ultrasonic welding stacks and configured to cause the firstwelding surface to move relative to the second welding surface; one ormore controllers operatively coupled to the first and second ultrasonicwelding stacks and to the actuator assembly, the one or more controllersoperatively being configured to: cause the actuator assembly to urge thefirst and second welding surfaces of the first and second horns towardone another until contacting the part, and thereby apply toward the parta first ultrasonic energy via the first horn and a second ultrasonicenergy via the second horn such that a frequency and a phase of thefirst and second ultrasonic energies are synchronized as the first andsecond ultrasonic energies are applied on both sides of the partsimultaneously, to thereby the seal the part along the section.
 2. Thesystem of claim 1, wherein the frequency is between 15 kHz and 70 kHz.3. The system of claim 1, wherein the part is a gable top having adifferent number of layers arranged across a longitudinal direction ofthe gable top.
 4. The system of claim 1, wherein the part is a gable tophaving a different number of layers arranged across a directiontransverse to a longitudinal direction of the gable top.
 5. The systemof claim 1, wherein an amplitude of the first ultrasonic energy differsfrom an amplitude of the second ultrasonic energy.
 6. The system ofclaim 1, further comprising a first generator generating the firstultrasonic energy and a second generator generating the secondultrasonic energy, wherein the first generator is designated as a mastergenerator that auto-locks feedback from the first ultrasonic weldingstack using a phase lock loop and instructs the second generator thatacts as a slave generator to match its own phase and frequency to thoseof the first generator.
 7. The system of claim 1, wherein the part iscomposed of a material that includes a polymeric film, a thermoplasticmaterial, a non-woven material, a metal foil, or a metal.
 8. The systemof claim 1, wherein the part is a pillow pack having an end portionhaving a different number of layers arranged across a longitudinaldirection of the end portion.
 9. The system of claim 1, wherein the partincludes a different number of layers that includes, along the sectionof the part to be sealed, a first number of layers in a first portion ofthe section and a second number of layers in a second portion of thesection, the first number differing from the second number.
 10. Anultrasonic welding method for sealing together multiple layers of apart, the method comprising the steps of: moving a first welding surfaceof a first horn toward an opposing a second welding surface of a secondhorn to close a gap between the first welding surface and the secondwelding surface until the first and second welding surfaces contact apart to be sealed along a section thereof; responsive to contacting thepart, applying to the part a first ultrasonic energy via the first hornand a second ultrasonic energy via the second horn such that a frequencyand a phase of the first and second ultrasonic energies are synchronizedas the first and second ultrasonic energies are applied on both sides ofthe part simultaneously, to thereby seal the part along the section, thefirst and second horns being arranged to point toward one another. 11.The method of claim 10, further comprising, responsive to sealing thelayers together, retracting the first horn relative to the second hornto release the part.
 12. The method of claim 10, wherein the frequencyis between 15 kHz and 70 kHz.
 13. The method of claim 12, wherein themoving is caused by a rotational movement of the first horn rotating atthe same speed as a rotational movement of the second horn.
 14. Themethod of claim 10, wherein an amplitude of the first ultrasonic energydiffers from an amplitude of the second ultrasonic energy.
 15. Anapparatus having at least one seal applied by the method of claim 10.16. The apparatus of claim 15, wherein the apparatus is a pillow pack ora carton or a pouch.
 17. The apparatus of claim 1, wherein the part is aspout to be sealed to a pouch.
 18. The apparatus of claim 1, wherein thefirst horn is a rotary horn and the second horn is a rotary horn, andthe controller is further configured to rotate the first horn and thesecond horn at the same rotational speed while applying the synchronizedfirst and second ultrasonic energies to the part.
 19. The apparatus ofclaim 6, wherein the first generator includes a first output and asecond output, the first output being operatively connected to a firsttransducer and the second output being operatively connected to a secondtransducer, the first transducer being operatively connected to thefirst horn and the second transducer being operatively connected to thesecond horn.
 20. The apparatus of claim 7, wherein an area of the partto be joined by far-field welding is at least ¼ inch or 6 mm away fromthe first welding surface of the first horn or from the second weldingsurface of the second horn.